Nerve Velocity Concuctio tests accuracy

Beginning 22 March, 2004, I have had several episodes od major edema from just above both knees to about ankle. ONLY during the first episode did I have SEVERE pain across the middle of both knees. No pain, ache, or anything else since March, 2004. The edema lasts approximately 12 days each episode. After the first I had a considerable loss of strength in both legs. Following an episode in December, 2004, my left knee will "buckle" amd roll out from under me. Tests show some atrophy in thigh. The nerve tests show "...withing normal limits".  Because of this, I am getting DX like ".. maybe it is arthritis".  I have no sensation from just above the left knee to just below the hip joint.  If it isn't Femoral Nerve Dysfunction, what else could it be?